Resumen de Distribución de temperatura y velocidad de embalses: análisis numérico-experimental aplicado a los embalses de Sau (Ter) y Ribarroja (Ebro)
Marina Arbat Bofill
The presence of a reservoir and its construction generate a direct impact in the rivers and in the surrounding landscape. The effects of the existing reservoirs, plus the combination of these with power plants (that use river water for cooling) or with the effects of the Climate Change, can cause significant changes in the thermal behavior of the river and, consequently, in the inhabiting communities. Water temperature is one of the most important variables of limnology studies: changes in the vertical temperature profile of a system modify the density of water and hence the stratification patterns. Most of the physical, chemical and biological processes that take place in a reservoir are controlled by the hydrodynamic and thermal evolution. The water temperature is the protagonist of this thesis because it is the key factor in most of the physical, chemical and biological processes occurring in aquatic ecosystems. The hydrodynamic model of a reservoir has to provide information about its complexity, for example, water stratification, mixing processes and water velocities. The initial knowledge of the system hydrodynamics is also necessary to carry out studies of water quality. The hydrodynamic performance is critical in terms of suspended sediment transport, dissolved contaminants or biological processes. In summary, the study of the hydrodynamic evolution of a reservoir is useful to know the quality of the stored water. This thesis has also furthered the knowledge of the hydrodynamic and thermal behavior of reservoirs. First of all a field data has been gathered, showing the hydrodynamic and thermal behavior of two catalonian reservoirs: Ribarroja Reservoir (Ebro River) and Sau Reservoir (Ter River). Both reservoirs are similar but differ in morphology, hidrology, water level, management criteria, sediment transport or in the presence of invasive species. Besides experimentally studying Ribarroja and Sau reservoirs by taking field data, in both cases the study has been supported by 2D and 3D numerical modeling. Numerical models of reservoirs are a useful tool for studying the behavior of the reservoirs as well as for predicting water quality and for managing the dam. After studying the thermal and hydrodynamic behavior of the reservoirs, numerical models have been applied to determine the thermal evolution in the length and depth of the studied reservoirs. For doing this CE-QUAL-W2 (Cole & Wells, 2008) model has been used, presenting good data fit to the data field campaigns. Noting that the 2D simulation using CE-QUAL-W2 was not capturing the complex 3D hydrodynamicas of the Ebro-Segre Rivers confluence in the tail of Ribarroja reservoir, it has been studied using a 3D model. FreeFlow (Cea et al., 2008) is the 3D hydrodynamic model used in which, in the context of this thesis, a surface heat module has been added in order to compute the surface heat balance based on meteorological data.
